Problem: test file not correctly named

Solution: move and split example_add.cpp

tests/socket.cpp

@@ -0,0 +1,9 @@
+#include <gtest/gtest.h>
+#include <zmq.hpp>
+
+TEST(socket, create_destroy)
+{
+    zmq::context_t context;
+    zmq::socket_t socket(context, ZMQ_ROUTER);
+}
+